I recall seeing articles about a scheme using DNA for authentication, where they make ink containing your DNA, and later you can distinguish an authentic signature from a counterfeit by having them test the ink.

But I don't remember the companies, and I had the impression it was mainly for expensive collectable things that tend to be counterfeited a lot (sports memorabilia, etc.).

A blood sample on the print would be verifiably unique, but the verification would require destructive testing of at least a portion of the sample. Perhaps you could put a drop of blood on an attached Certificate of Authenticity to avoid having to damage the print itself.